BERLIN – German authorities banned three ultraconservative Islamic groups Wednesday, including one whose Internet propaganda videos helped inspire the extremist who killed two American airmen at Frankfurt airport in 2011, the country's domestic intelligence chief said.

Police launched early morning raids on 21 apartments and one meeting room belonging to DawaFFM, Islamic Audios and al-Nussrah — all of which adhere to the hardcore conservative Salafi interpretation of Islam.

The groups were largely involved in recruitment, fundraising and propaganda, including videos and other postings urging people to fight against those who did not believe in their version of Islam, said Hans-Georg Maassen, the head of Germany's domestic intelligence service, the Office for the Protection of the Constitution.

"These organizations are oriented against the basic right to freedom of religion — against Christians and other faiths including Shiites," Maassen said.

For example, he said, in one DawaFFM YouTube posting, an Arabic speaker told Shiite Muslims: "If the Prophet Muhammad heard your words he'd hack off your hands and feet and banish you from the earth."

It was also DawaFFM YouTube videos and Facebook postings that helped radicalize Arid Uka — the lone-wolf attacker who killed two U.S. airmen and injured two others at the Frankfurt Airport in 2011, Maassen said.

Uka was convicted of murder last year and sentenced to life in prison.

The Salafi movement in Germany has been growing quickly, attracting both Muslims and converts, primarily men between ages 20 and 30. In 2011 there were some 3,800 people Salafis known to authorities and there are now some 4,500.

Some 70 percent are Germans and 30 percent are non-Germans, coming from a variety of nations including Turkey, Morocco and Bosnia, according to a security official who was only allowed to discuss the figures on condition of anonymity. About a quarter are Muslim converts.

They have been under close observation since 2010, but that was stepped up further last year after they clashed with police in Bonn last year at a far-right demonstration.

Following the incident, a known German-born terrorist who is now based in Pakistan's border area with Afghanistan called on Salafis in Germany to kill members of the far-right group as well as employees of Der Spiegel magazine, which printed photos of the demonstrators holding Prophet Muhammad signs.

"We have determined that in the past year the Salafis have begun acting not only aggressively and militantly in their prayer rooms or on the Internet but also violently on the streets," Maassen said.

Already last summer, Interior Minister Hans-Peter Friedrich banned the Salafi organization Millatu Ibrahim, of which al-Nussrah was a splinter group, and opened the investigation of DawaFFM.

He said Wednesday's move to extend the ban should be seen as a "clear sign against those who practice exclusion, violence and intolerance."